I take it the clear coat you buy in a can at Autozone is not the same

[Qualitywires.com]

is not the same as the proffessionals use? I sprayed some small plastic parts and the clear coat I used seems to peel off real easy.

 

[TSR6]

It depends on the clear-coat you bought, and what you sprayed it on.

Some paints just will not stick to plastic, and with the slightest flex will chip/peal away. You'll need a spray can that is made for plastic.